From: Rasmus Villemoes Date: Wed, 21 Apr 2021 19:46:36 +0000 (+0200) Subject: efi: cper: fix snprintf() use in cper_dimm_err_location() X-Git-Tag: v4.4.272~23 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=acc1b80d0d4b9821b4a1b29c4b22419fe279de01;p=thirdparty%2Fkernel%2Fstable.git efi: cper: fix snprintf() use in cper_dimm_err_location() [ Upstream commit 942859d969de7f6f7f2659a79237a758b42782da ] snprintf() should be given the full buffer size, not one less. And it guarantees nul-termination, so doing it manually afterwards is pointless. It's even potentially harmful (though probably not in practice because CPER_REC_LEN is 256), due to the "return how much would have been written had the buffer been big enough" semantics. I.e., if the bank and/or device strings are long enough that the "DIMM location ..." output gets truncated, writing to msg[n] is a buffer overflow. Signed-off-by: Rasmus Villemoes Fixes: 3760cd20402d4 ("CPER: Adjust code flow of some functions") Signed-off-by: Ard Biesheuvel Signed-off-by: Sasha Levin --- diff --git a/drivers/firmware/efi/cper.c b/drivers/firmware/efi/cper.c index c0e54396f2502..dc8d2603612ed 100644 --- a/drivers/firmware/efi/cper.c +++ b/drivers/firmware/efi/cper.c @@ -257,8 +257,7 @@ static int cper_dimm_err_location(struct cper_mem_err_compact *mem, char *msg) if (!msg || !(mem->validation_bits & CPER_MEM_VALID_MODULE_HANDLE)) return 0; - n = 0; - len = CPER_REC_LEN - 1; + len = CPER_REC_LEN; dmi_memdev_name(mem->mem_dev_handle, &bank, &device); if (bank && device) n = snprintf(msg, len, "DIMM location: %s %s ", bank, device); @@ -267,7 +266,6 @@ static int cper_dimm_err_location(struct cper_mem_err_compact *mem, char *msg) "DIMM location: not present. DMI handle: 0x%.4x ", mem->mem_dev_handle); - msg[n] = '\0'; return n; }